RabbitMQ MQTT 5: inapplicable PUBLISH property disconnects matching subscribers

Summary

RabbitMQ is a messaging and streaming broker. From 3.13.0 until 3.13.19, 4.0.24, 4.1.15, 4.2.10, and 4.3.5, the MQTT 5 parser in deps/rabbitmq_mqtt/src/rabbit_mqtt_packet.erl accepts Request-Problem-Information on PUBLISH packets even though the property is valid only for CONNECT. An authenticated publisher with topic write permission can cause the broker to store and route that inapplicable property to a separately authenticated matching subscriber. When the subscriber path serializes the outbound PUBLISH, serialise_prop/2 has no matching clause, and the uncontained function_clause exception closes the victim MQTT or Web MQTT connection. The publisher connection and broker remain available, and queued replay, retained-message persistence, and broker-wide denial of service were not established. This issue is fixed in versions 3.13.19, 4.0.24, 4.1.15, 4.2.10, and 4.3.5.

Timeline

1. Oct 14, 2026, 4:07 PM UTCCVE published
2. Oct 14, 2026, 5:52 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Oct 14, 2026, 5:53 PM UTCRecord last updated

Affected versions

• rabbitmq rabbitmq-server

  From 3.13.0 · fixed in 3.13.19; From 4.0.0 · fixed in 4.0.24; From 4.1.0 · fixed in 4.1.15; From 4.2.0 · fixed in 4.2.10; From 4.3.0 · fixed in 4.3.5

• rabbitmqBitnami

  From 3.13.0 · fixed in 3.13.19; From 4.0.0 · fixed in 4.0.24; From 4.1.0 · fixed in 4.1.15; From 4.2.0 · fixed in 4.2.10; From 4.3.0 · fixed in 4.3.5

References 6